The present inventions relate to a variable speed transmission arrangement with an infinitely variable toroidal drive and a planetary summing gear arrangement including a central shaft extending through the toroidal drive for direct power transmission through the transmission arrangement.
U.S. Pat. No. 6,059,685 discloses a variable speed transmission arrangement, in which the toroidal drive includes a the two-chamber arrangement, whereby the central shaft drivable from a drive motor or engine is connected to a first central wheel and, at its end, to a second drive-side central wheel of the toroidal drive. The second central wheel is arranged coaxially to the central shaft and, with respect to its toroidal friction surface, mirror-symmetrically to the first drive-side central wheel, and is connected directly to the planet carrier of the toroidal drive. The first and second drive-side central wheels of the toroidal drive are in engagement in a known way by means of their friction surfaces, via intermediate wheels arranged pivotably for a change of the transmission ratio, with the toroidal friction surfaces of an output central wheel of the toroidal drive. The output central wheel is arranged coaxially to and in the center region of the central shaft and the central shaft passes with play through the second central wheel. The output central wheel is connected fixedly in terms of rotation, by means of an intermediate shaft which is concentric to the central shaft directly to the sun wheel of a summing gear set. The sun wheel meshes with main planet wheels mounted on the planet carrier via bearing bolts. Secondary planet wheels mounted on the planet carrier mesh both with the main planet wheels and with a ring wheel. The ring wheel is connected by means of an associated clutch to a gear member of a follow-up gear set of the planet wheel type, the sun wheel of which is stationary with respect to the transmission case. In this instance, the assignment between the summing gear set and the follow-up gear set is such that, on the one hand, the ring wheel of the summing gear set can be coupled to the planet carrier of the follow-up gear set. Then the planet carrier supports the double planet wheels and is connected for rotation with an output shaft, arranged coaxially to the central shaft, of the variable speed transmission arrangement. On the other hand, the sun wheel of the summing gear set can be connected for rotation with the sun wheel of the follow-up gear set via an associated clutch.
This known variable speed transmission arrangement is disclosed in the publication only in the form of a basic transmission diagram, without structural and functional solution details.
DE 100 46 926 A1 discloses a further generic variable speed transmission arrangement, in which a central shaft passes with play through a central wheel of an infinitely variable toroidal drive. The central wheel has a toroidal friction surface on one end face, and is connected fixedly in terms of rotation, at its shaft end lying adjacently to the other end face of the central wheel, to a planet carrier of a summing gear set of the planet wheel type. A direct mutual rotationally fixed drive connection is likewise provided for the central wheel and the planet carrier, and is designed in such a way that the central wheel has coupling members projecting axially from its other end face. The planet carrier has corresponding counter-coupling members projecting axially from this adjacent end face. The axial overall length of this known variable speed transmission arrangement is increased due to these coupling members which are in rotationally fixed engagement with one another. The central shaft of this arrangement passes with play, at its other shaft end, through a second central wheel of the two-chamber toroidal drive, the second central wheel being arranged, with respect to its toroidal friction surface, mirror-symmetrically to the first central wheel, and connected directly to the planet carrier, of the toroidal drive. The second central wheel of the toroidal drive is in this case arranged coaxially, displaceably and fixedly in terms of rotation with respect to the central shaft. For the rotationally fixed arrangement intermediate coupling members in the form of rolling balls engage simultaneously outer axial coupling grooves on the inner circumference of the central wheel and radially aligned inner axial coupling grooves on the outer circumference of the central shaft. Owing to their short distance from the axis of rotation of the central shaft, the intermediate coupling members are stressed to the maximum by the torque of the second central wheel and are thereby restricted particularly in terms of their useful life. The central shaft of this known arrangement is connected releasably in a complicated way to the planet carrier of the summing gear set, for which purpose the central shaft has, on the outer circumference of its respective shaft end, an axial take-up toothing, engaged by a corresponding axial take-up toothing on the inner circumference of a hub which is arranged concentrically to the shaft end and which is connected for rotation with the planet carrier. In order to absorb the axial forces exerted on the planet carrier via the adjacent input-side central wheel of the toroidal drive, the hub of the planet carrier is supported against the securing ring inserted into a circumferential groove of the shaft end of the central shaft. The cross-section of the central shaft is appreciably weakened by the axial take-up toothing and the circumferential groove. Furthermore, because of the high torques to be transmitted on a small radius to the axis of rotation of the central shaft, these axial take-up toothings must be long in the directions of the axis of rotation. If the take-up toothings are arranged so as to be axially offset to the wheel set of the summing gear set, the overall length of the variable speed transmission arrangement would be appreciably increased. In order to avoid this, the hub of the planet carrier in this known arrangement is arranged concentrically within the wheel set of the summing gear set and, together with the wheel set, in the same axial region of the axis of rotation of the central shaft, although, as a result of this, the diameter ratios of the wheel set are necessarily affected and, consequently, the selection of the transmission ratios of the variable speed transmission arrangement is highly restricted.
It is the object of the present invention to provide a variable speed transmission arrangement of short axial overall length, which is easy to assemble, includes a one-part transmission case, a small number of components, low weight and a low manufacturing costs.